Photographic tanning development agent precursor in light-sensitive element

ABSTRACT

Light-sensitive photographic materials are provided in the light-sensitive silver halide emulsion layer or in a separate colloid layer in water-permeable relationship with the emulsion layer, with a tanning development agent precursor constituted by an O-dihydroxybenzene derivative having at least one of its hydroxyl groups esterified to form a halogenated acyloxy group or etherified to form an Alpha -tetrahydropyranyloxy group. Such precursor compounds are stable during storage and do not result in discoloration of the emulsion layer. On treatment with an alkaline activating liquid, a tanning photographic developing agent is released. The O-dihydroxybenzene derivatives per se are also disclosed.

United States atent us] shame Verelst at al. 51 Feb. 1, 1972 [54] PHOTOGRAPH: TANNING Reterences Cited DEVELOPMENT AGENT PRECURSOR UNITED STATES PATENTS KN LIGHT-SENSITIVE ELEMENT 3,246,988 4/1966 Porter et a1. ..96/95 X [72] lnventora: Johan Lodewijk Verelst, Kontich; Jozel 3,297,445 1/1967 Duennebier et a1 ..96/66 X Frans Willems, Wilrijk; Raymond Leopold We ssmt Estee Assignee: Gevaert-Agla N.V., Mortsel, Belgium 7' Filed: July 19, 1968 Appl. No.: 745,979

Foreign Application Priority Data July 19, 1967 Great Britain ..33,260/67 July 19, 1967 Great Britain.

...96/95, 96/63, 96/66 ..G03c 1/06 Field oi Search ..96/95, 76, 66, 63

Primary Examiner-Norman G. Torchin Assistant Examiner.lohn L. Goodrow Att0rney-William J. Daniel [5 7] ABSTRACT not result in discoloration of the emulsion layer. On treatment with an alkaline activating liquid, a tanning photographic developing agent is released. The O-dihydroxybenzene derivatives per se are also disclosed.

10 Claims, No Drawings PHOTOGRAPHIC TANNING DEVELOPMENT AGENT PRECUJRSOR IN LIGHT-SENSITIVE ELEMENT The present invention relates to light-sensitive silver halide emulsions for use in photography, and particularly to substantially unhardened gelatino-silver halide emulsions of use in photographic processes which bring about local hardening or tanning of the silver halide emulsion layers by treatment of the emulsion layers in alkaline solution, and also relates to developing agent precursors suitable for use in such photographic emulsions.

It is known to incorporate gelatin-tanning developing substances into the silver halide containing layer of a photographic material and to develop the exposed material by treating the silver halide emulsion layer with an alkaline solution activating the development. Most of the known gelatintanning silver halide developing agents, however, cannot be used for this purpose. For instance, pyrocatechol and pyrogallol are very active tanning developing agents but are very unstable when incorporated in an unhardened gelatino-silver ha lide emulsion and promote fog, form spots or cause desensitization. It has been observed that when keeping a photographic material containing pyrogallol or pyrocatechol for a certain time, discoloration of the gelatino-silver halide emulsion layer and occasionally of the paper support occurs. The discoloration is not uniform all over the surface but stained and tends to be intense on the margins of the light-sensitive element. Such stained material is no longer suited for reflectographic exposure through the back of the support since it does not transmit the light uniformly. On the areas corresponding with the stains the emulsion isless exposed and after tanning development thus less hardened. If this tanning developed material is used for producing a gelatin relief image, the parts of the emulsion corresponding to the stained areas, which are exposed too little and not completely hardened, are partially removed when washing away the unhardened parts of the emulsion layer. When transferring the weak gelatin of such a tanning developed emulsion layer to another support, e.g., paper, by pressing the layer against said support, an irregular transfer is realized.

Furthermore, some silver halide developing agents, such as hydroquinone, vary appreciably in their gelatin-tanning activity depending upon the conditions of usage such as the sulfite concentration.

Moreover, hydroquinone, which does not give rise to the above-mentioned discoloration, shows the great disadvantage with regard to pyrocatechol and pyrogallol of having less selective tanning action. The unsharp hardening is the principal reason why it is not used as tanning developer on a large scale.

In order to overcome the disadvantage of the abovetanning developers it has been proposed in British Pat. No. 812,673 to form a photographic material, suitable for making relief images, by incorporating an organic or substantially water-insoluble inorganic ester of a polyhydroxybenzene compound in at least one colloid layer comprised by the photographic material. Although these tanning-developer precursor compounds have a high stability in the emulsion layer and the absence of reducing functions in their molecule whereby any marked adverse influence upon the light-sensitive silver halide emulsion is excluded, they show the disadvantage of being hydrolyzed only very slowly in the alkaline activating bath so that a delay in release of active developer and thus in development is involved.

lt has now been found that mono-wtetrahydropyranyl ethers of o-dihydroxybenzenes and haloacylesters of odihydroxybenzenes possess outstanding properties as so-called tanning developing agent precursors for silver halide emulsions particularly for use in unhardened silver halide emulsion layers.

By the term developing agent precursor is to be'understood developing agents having no developing action before the development is actually desired. When the developer precursor compounds of the invention are treated with aqueous baths, particularly with alkaline aqueous baths the atetrahydropyranyl ether group or the haloacyl ester group(s) is (are) split off by hydrolysis and the original, actual develop ing agent is set free. Since the compounds of the invention have no developing action before the development is actually desired the emulsion layers containing said compounds are stable against staining.

Thus, in accordance with the invention a photographic element is provided comprising a support and at least one lightsensitive silver halide emulsion layer and integral with said photographic element i.e., in a lightsensitive emulsion layer and/or in a colloid layer in water-permeable relationship therewith an o-dihydroxybenzene developing agent precursor wherein at least one of the hydroxyl groups of said o-dihydroxybenzene has been esterified to form a hydrolyzable halogenated acyloxy group or wherein one of the hydroxyl groups has been ethcrified to form a hydrolyzable atetrahydropyranyloxy group.

More particularly, in accordance with the present invention a photographic element is provided comprising a support and at least one light-sensitive silver halide emulsion layer and integral with said photographic element at least one compound corresponding to the general formula:

wherein:

R represents a haloacyl group such as chloroacetyl, dichloroacetyl, trichloroacetyl, bromoacetyl, fluoroacetyl, difluoroacetyl, trifluoroacetyl, aor B- chloropropionyl, B-dichloropropionyl, fi-trichloropropionyl, etc., or an a-tetrahydropyranyl group provided R is hydrogen,

R stands for hydrogen or a haloacyl group such as those exemplified for R R represents a hydrogen atom, an alkyl group such as methyl and ethyl, including a substituted alkyl group, a halogen atom such as chlorine and bromine, an alkoxy group such as methoxy and ethoxy, or the group --OR wherein R: has the same significance as above.

The present invention also provides a process for tanning developing a photographic silver image in a silver halide emul sion layer comprising a hardenable colloid by incorporating in said emulsion layer and/or in a colloid layer in water-permeable relationship with said emulsion layer e.g., an undercoat or overcoat for such emulsion layer, a developer precursor compound as defined above and by carrying out the development by means of an alkali solution.

According to the present invention it is possible to prepare relief images by using a photographic material which is tanning-developable by the presence therein of a tanning developer precursor compound according to the invention and the use of an alkali solution to activate said development.

The tanning developing agent precursors according to the invention possess the favorable combination of properties of high activity as gelatin'tanning silver halide developing agents, good stability and low solubility in water.

The compounds of use according to the present invention possess the further advantageous characteristic that when they are used in hardenable silver halide emulsion layers the emulsions are very stable and may be stored for extended periods of time without becoming hardened. In the presence of aqueous alkali, these halogenated esters hydrolyze readily to yield the corresponding active gelatin-tanning silver 'halide developing agents so that no delay in development is involved. The images obtained are free from spots, do not show fog or defects caused by desensitization and possess the desired sensitivity and gradation with normal length .of development time,

As a result of their low solubility in water, diffusion to an adjacent layer in the photographic element is prevented.

Examples of tanning-developer precursors of use according to the present invention are:

3. OCOCHQCHQCI 4. Cl

OCOCH-CH3 OH @OH 5. ocoomoi e. OCOCFa Q-oooomm @oooom 7. (|)COCH2C1 8. ooocmoi @ocoomci oooomoi l l 1IaC-(T--CII CHg(CHz)2C/Ha .1 (ROOCIIQCI 10. 000011201 The following preparations illustrate how the compounds according to the above general formula can be prepared. Preparation 1: Compound 1 To 110 g. (1 mole) of pyrocatechol in 1 liter of anhydrous benzene 90.4 g. (0.8 mole) of chloroacetyl chloride are added dropwise while stirring and refluxing the mixture. After having refluxed for 50 hours the evolution of hydrogen chloride has nearly come to an end. The precipitate obtained upon cooling is stirred with 1 liter of water and recrystallized from benzene. Yield: 67 g. (47 percent). Melting point: 84 C.

Preparation 2: Compound 2 To 55 g. (0.5 mole) of pyrocatechol in 500 ml. of anhydrous benzene 62 g. (0.4 mole) of bromoacetyl chloride are added dropwise while stirring and refluxing the mixture. After having refluxed for 40 hours the evolution of hydrogen chloride has nearly come to an end. The residue obtained after evaporation is stirred with 200 ml. of cold water. The product is recrystallized from 600 ml. of cyclohexane. Yield: 47 g. (50 percent). Melting point: 72-74 C.

Preparation 3: Compound 3 To 55 g. (0.5 mole) of pyrocatechol in 500 ml. of anhydrous benzene 50.8 g. (0.4 mole) of B-chloropropionyl chloride are added dropwise in 30 min. while stirring and refluxing the mixture. After having refluxed for 27 hours the evolution of hydrogen chloride has nearly come to an end. The oil obtained after evaporation of the reaction mixture becomes solid by stirring with 150 ml. of water. The product is recrystallized from 1 liter of cyclohexane. Yield 62 g. (77 percent). Melting point: 50 C. Preparation 4 Compound 4 To 55 g. (0.5 mole) ofpyrocatechol and 12.15 g. (0.5 mole) of magnesium curlings in 500 ml. of anhydrous benzene 50.8 g. (0.4 mole) of a-chloropropionyl chloride are added dropwise in 30 min. while stirring and refluxing the mixture. After having refluxed for 21 hours the evolution of hydrogen chloride has nearly come to an end. The oil obtained after evaporation of the reaction filtrate is distilled. Yield: 45 g. (56 percent). Boiling point: 96-98 C./0.1 mm. Preparation 5: Compound 5 To 1 10 g. (1 mole) of pyrocatechol and 24.3 g. (1 mole) of magnesium curlings in 1 liter of anhydrous benzene 248.6 g. (2.2 moles) of chloroacetyl chloride are added dropwise in 1 hour while stirring and refluxing the mixture. After having refluxed the mixture for 17 hours the evolution of hydrogen chloride has nearly come to an end. The oil obtained after evaporation of the reaction filtrate is poured into water and the precipitate formed is filtered. The product is recrystallized from a mixture of methanol and water (5:1 Yield: 163 g. (62 percent). Melting point: 56 C. Preparation 6: Compound 6 To 22 g. (0.2 mole) of molten pyrocatechol 92.5 g. (0.44 mole) of trifluoroacetic anhydride are added dropwise in 3 hours in such a way that the reaction mixture refluxes gently. The reaction mixture is kept for 4 hours at 120 C. The mixture is distilled twice under reduced pressure of a water jet pump. Yield: 45 g. (75 percent). Boiling point: 86 C./15 mm. Preparation 7: Compound 7 To 41.5 g. (0.25 mole) of 4-tert.butyl-pyrocatechol in 600 m1. of anhydrous benzene 62.15 g. (0.55 mole) of chloroacetyl chloride are added dropwise in 20 min. while stirring and refluxing the mixture. After having refluxed for 50 hours the evolution of hydrogen chloride has nearly come to an end. The oil obtained after evaporation of the reaction mixture is crystallized in hexane, and the precipitate is washed with water. Yield: 45 g. (56 percent). Melting point: 78 C. Preparation 8: Compound 8 To 41.5 g. (0.25 mole) of 4-butyl-pyrocatechol and 6 g. (0.25 mole) of magnesium curlings in 600 ml. of anhydrous benzene 62.15 g. (0.55 mole) of chloroacetyl chloride are added dropwise in 30 min. while stirring and refluxing the mixture. After having refluxed for 17 hours the evolution of hydrogen chloride has nearly come to an end. The oil obtained after evaporation of the reaction filtrate is distilled. Yield: 51 g. (64 percent). Boiling point: 173l 77 C./0.6 mm. Preparation 9: Compound 9 To 31.5 g. (0.25 mole) of pyrogallol in 750 ml. of anhydrous .toluene 22.6 g. (0.2 mole) of chloroacetyl chloride are added dropwise in 30 min. while stirring and refluxing the mixture. After having refluxed for 37 hours the evolution of hydrogen chloride has nearly come to an end. After cooling, the unreacted pyrogallol is filtered off. The viscous residue of the evaporated filtrate is dissolved in chloroform. Upon cooling 8 g. of pyrogallol-monochloroacetate are obtained having a melting point of 100 C.

I Preparation 10: Compound 10 The procedure of preparation 9 is repeated with the difference however, that the chloroform solution is evaporated and the residue is kneaded with water. The undissolved residue is dried and recrystallized from benzene. Yield: 6.5 g. Melting poing t C.

Preparation 1 1: Compound 1 1 To 31.5 g. (0.25 mole) of pyrogallol in 750 ml. of anhydrous toluene 96 g. (0.85 mole) of chloroacetyl chloride are added dropwise while stirring and refluxing the mixture. After having refluxed for 82 hours the evolution of hydrogen chloride has nearly come to an end. The viscous residue obtained after evaporation of the reaction mixture becomes solid by treatment with water. The product is recrystallized from a mixture of benzene and hexane. Yield: 49 g. (54 percent). Melting Preparation 12: Compound 12 The mono-a-tetrahydropyranyl ether of pyrocatechol was prepared as follows:

To 1 g. (1 mole) of pyrocatechol in 700 ml. of anhydrous toluene a solution of 84 g. (1 mole) of 2H-3,4-dihydropyran in 700 ml. of toluene was added dropwise while stirring and refluxing the mixture. The mixture was refluxed for 15 hours and then evaporated till dry. Yield: 184 g. (95 percent).

As will hereinafter be referred to, the invention is particularly suitable for application in the tanning development of silver halide emulsion layers of light-sensitive photographic material, for example in the course of preparing relief images or in the course of preparing hectographic masters by physical transfer or unhardened emulsion parts to a dye sheet.

In referring to silver halide emulsion layers we particularly have in mind gelatino-silver halide emulsion layers. However, the invention is also applicable in the development of silver halide emulsions having other hydrophilic colloid binders, provided said colloids are hardenable by the oxidation products of polyhydroxybenzene compounds. Thus as colloid may be used for example, gelatin and other proteinaceous bin ders such as casein, albumin, and zein as well as the hardenable derivatives thereof, which binders may be partly replaced by other layer forming substances e.g., cellulose derivatives such as carboxymethyl cellulose, polyvinyl alcohol, polyvinyl acetate, polyvinyl acetal, partially hydrolyzed polyvinyl acetates, alginates, polyvinyl pyrrolidone, etc.

The invention is also applicable in processes in which the selective or imagewise hardening required is a selective hardening of a nonlight-sensitive layer. We refer for instance to the performance of the so-callcd silver complex diffusion transfer processes. Such a process can be performed using a single multilayer material comprising in addition to the lightsensitive layer an image-receiving colloid layer into which complexed silver halide can diffuse from the unexposed parts of the silver halide layer. The diffusing silver salt is converted into a visible image in the receiving layer, e.g., under the action of development nuclei which may be incorporated in such layer. As an alternative, an image-receiving material separate from the light-sensitive material may be used, by pressing the exposed light-sensitive material into contact with the image receiving material in the presence of developer and sub sequently stripping the materials apart. if in a diffusion transfer process it is required to form a tanning developed image in the image-receiving layer this result can be achieved by means of the invention i.e., by carrying out the development with an alkaline solution, the developing agent precursor(s) of the invention being e.g., incorporated into the imagereceiving layer.

The tanning development according to the present invention gives favorable results in the preparation of etching resists by means of so-called photogravure films e.g., as described in U.K. Pat. Nos. 1,035,441, 938,960 and 1,070,795 and in Belgian Pat. No. 690,925.

Photogravure film generally comprises in order of sequence a hydrophobic flexible support, a stripping layer, a hydrophobic flexible membrane and a light-sensitive silver halide emulsion layer containing hardenable hydrophilic colloid such as gelatin or another protein. The photogravure film may contain additional layers such as an antihalation layer, a back layer, a protective covering layer, etc.

Etching resists for making gravure plates or cylinders may be produced e.g., by the following steps:

The metal surface can now be etched by means of the common etching solutions.

The tanning development according to the invention is also applicable in the preparation of stencils for screen printing in a photographic way.

Screen printing film generally comprises in order of sequence, a flexible support, a stripping layer, a subbing layer and one or more light-sensitive silver halide emulsion'layers containing hardenable hydrophilic colloid such as gelatin.

Screen printing stencils may be produced e.g., by the following steps:

1. the light-sensitive material is exposed to a line original,

2. the exposed material is tanning developed and the unhardened areas are removed by washing with water,

3. the material is pressed with the emulsion-side against a screen e.g., Japan paper or a woven tissue and after drying the flexible support is stripped off.

The screen imagewise covered with hardened gelatin can now be used as screen printing stencil.

The silver halide emulsions comprising tanning developing agents according to the invention are also very useful in the preparation of continuous tone-gelatin relief images for use in the well-known dye imbitition printing processes wherein color-separation negatives are prepared in a well-known manner, then each negative is printed through the support onto a film according to the invention having an unhardened gelatino-silver halide emulsion layer, followed by washing out the unexposed emulsion areas, dyeing the resulting positive gelatin matrices and making imbibition dye prints therefrom. In a variation of this procedure, the unhardened gelatinosilver halide emulsion layers of the invention containing the indicated developing agents may be exposed directly to a colored subject such as a positive color transparency and the gelatin color-separation matrices are prepared therefrom by reversal methods.

Further the tanning development according to the present invention gives favorable results in the manufacture of hectographic masters e.g., as described in UK. Pat. Nos. 981,508, 996,963, and 804,076. According to these processes, the unhardened gelatin parts of the tanning developed emulsion layer are easily and selectively transferred to another support e.g., paper, by pressing said layer against said support. The present invention offers the important advantage that the hardening is strictly localized corresponding to the exposed areas, which is especially important in the reproduction of documents and drawings and in halftone work. According to the invention masters for spirit duplicating are obtained with which a sharp reproduction of characters or lines having a line width smaller than 1 mm. is obtained.

A master sheet for a spirit duplicator may be produced e.g., by the following steps:

1. a latent image of an original is made on the gelatino-silver halide emulsion layer by reflectographic exposure through the back of the support;

2. the exposed emulsion layer is tanning developed and a positive legible image is obtained;

3. the tanning developed emulsion layer is pressed against a hectographic carbon paper and then both sheets stripped apart so that the unhardened gelatin covers the dyestuff layer of the carbon paper on the areas corresponding to the unexposed areas of the emulsion. layer.

The carbon paper is used as master sheet on a usual spirit duplicator for making legible positive prints.

Instead of using the carbon paper as the master sheet two further steps can be included namely:

4. the dyestuff layer of the carbon paper, imagewise covering this unhardened gelatin, is pressed against a sheet of art printing paper,

5. after a few minutes both sheets are separated.

The unhardened gelatin has been transferred to the art printing paper and has pulled out dyestuff from the dyestuff layer. The art printing paper which, after being separated from the carbon paper, carries a laterally reversed image of the original composed ofgelatin, which is covered with dyestuff, is used as hectographic master in a spirit duplicator.

Naturally, the tanning developing agents of the invention also find utility in conventionally hardened silver halide emulsion layers where their high stability is of advantage. Such emulsions are useful in conventional photographic processes where differential hardening of the emulsion layer is not essential. Development of such exposed emulsions is then initiated with simple alkaline solutions.

The tanning developing agents of the invention are also interesting for use in unhardened silver halide emulsion layers e.g., for continuous-tone and line work in order to eliminate the time-consuming fixing and washing operations. Here too development is initiated by simple alkaline solutions and the residual silver halide in the unexposed and thus unhardened areas can be washed away together with the unhardened gelatin. The result is that in the high light areas no stain and no fog is produced.

The tanning-developing agents according to the invention can be incorporated into the silver halide emulsion from a solution in a suitable solvent such as ethanol, tricresyl phosphate etc., or mixture of solvents or from a dispersion, which solution or dispersion is mixed with the emulsion. This addition may occur during no matter what step of emulsion preparation and preferably just before coating of the emulsion. The solution or dispersion of the tanning-developing agents may also first be homogeneously dispersed into a hydrophilic colloid composition e.g., aqueous gelatin whereupen the whole is mixed with the photographic emulsion. The preparation of such a dispersion of tanning-developing agent according to the invention in aqueous gelatin can be illustrated by the following preparation:

Preparation 13 150 g. of gelatin are swollen in 850 cc. of water and melted at 50-5S C. whereupon cc. of glacial acetic acid and 100 cc. of a solution of 5 g. of dioctyl sulphosuccinic acid sodium salt in 80 cc. of water and cc. of ethanol are added. While stirring thoroughly by means of a high-speed mixer a solution of 0.66 mole of tanning developer precursor in 200 cc. of ethanol and 100 cc. of tricresyl phosphate heated to 40-45 C. is added. Finally, water is added to bring the volume to 1,720 cc.

The tanning-developer precursor compounds of use according to the invention need not necessarily be incorporated into the light-sensitive silver halide emulsion layer itself; they may also be incorporated in another colloid layer in water-permeable relationship with the light-sensitive emulsion layer e.g., an undercoat or overcoat for such emulsion layer. The addition to the coating composition of such other colloid layer can occur in the same manner as described for the addition to the emulsion.

The concentration of tanning-developer precursor according to the present invention will vary markedly depending upon the particular chemical compound involved, the particular process in which the emulsion layer is to be used, and the location of the compound within the photographic element. When incorporated in the silver halide emulsion layer the amount is generally comprised between 0.1 mole and 2 moles per mole of silver halide. When incorporated in another colloid layer in water-permeable relationship with the emulsion layer somewhat larger concentrations can be used. The amount of gelatin in the emulsion can be varied within rather wide limits, depending somewhat upon the particular process in which the emulsion layer is to be used. The useful range is generally from about 150 g. to 1,000 g. of gelatin per mole of silver halide in the emulsion.

It is evident that other additives such as development accelerators, antifogging agents, stabilizers, sensitizers, antioxidizing agents, softeners for gelatin such as urea etc., may also be incorporated into the composition of the gelatino-silver halide emulsion layer or other water-permeable collide layer.

Examples of development accelerators which may be added to the emulsion layer or other water-permeable colloid layer are the polyoxyalkylenc derivatives such as those described in U.S. Pat. Nos. 2,531,832 and 2,533,990 and in UK. Pat. Nos.

920,637, 940,051, 945,340 and 991,608 as well as the amino- N-oxides as described in French Pat. No. 1,498,724.

The alkaline solutions for development of the photographic material incorporating the tanning development agents according to the present invention, can be of different composition. Although a simple alkaline solution, e.g., sodium hydroxide, potassium hydroxide, sodium carbonate, potassium earbonate, will suffice, it may be advisable to add some other additives such as wetting agents, a softener for the gelatin e.g., urea, preserving agents such as sodium sulfite, activators, silver halide solvents, etc.

It is evident that the alkaline activating solution may also contain development accelerators as referred to above, antifogging agents such as benzotriazole, I-phenyl-S-mercaptotetrazole, etc. These compounds however, are not essential for the tanning development according to the present invention.

The activator solutions can be applied to the exposed photographic element in any known way such as by dipping, spraying or other suitable surface applications.

The following examples illustrate the utility of the tanning developing agent precursors according to the invention in substantially unhardened gelatino-silver halide emulsions.

EXAMPLE 1 A. Composition of a screen printing film.

A screen printing film is prepared comprising successively the following layers: 1. A flexible support of cellulose triacetate.

2. A stripping layer, which has been applied pro rata of mg. of dry substances per sq. m. from the following composition:

cellulose nitrate S g. ethanol 360 cc.

diethyl ether 590 cc. n-butanol 50 cc.

triphenyl phosphate l g.

3. A subbing layer, which has been cast from the following composition pro rata of 200 mg. of dry substance per sq. m.:

gelatin 10 g. water 40 cc. acetic acid 4 cc.

methanol 960 cc.

4. A light-sensitive silver halide emulsion layer A which has been applied pro rata of 10-12 g. of solids per sq. m. from a dispersion having the following composition:

orthochromatic gclatino-silver bromide emulsion which comprises a yellow and a red screening dye, has an initial proportion of gelatin to silver nitrate of4 to l and has a high gradation 1,000 cc.

50% aqueous solution of urea 30 cc. 5% aqueous solution of tetradecyl sodium sulfate 10 cc.

water 80 cc.

20% aqueous solution of potassium metabisulfite 20 cc.

dispersion of compound l in aqueous gelatin prepared as .59E9JE was. Ene es B 5. A light-sensitive silver halide emulsion layer B which has been applied pro rata of 6-8 g. of solids per sq. m. from a dispersion having the following composition:

orthochromatic gelutino-silvcr bromide emulsion which comprises a yellow and a red screening dye, has an initial proportion of gelatin to silver nitrate of 5.2 to l and has a B. Formation of a screen printing stencil The screen printing film is exposed through a line diapositive and then treated in a 10 percent aqueous solution of sodium carbonate to initiate development. After having been treated in a 3 percent aqueous solution of acetic acid the material is washed with warm water of 45 C. in order to remove the unexposed and thus untanned areas.

The imagewise tanned and washed resist is affixed with the emulsion side to the screen material and dried. Subsequently the flexible cellulose triacetate support is removed by stripping. In this way, a screen printing stencil is obtained, the unexposed areas of which are entirely open.

ln a similar way, screen printing stencils were prepared using compounds 5, 7 and 12 as tanning developer precursor in the light-sensitive emulsion layers A and B.

EXAMPLE 2 A. Composition of a photogravure film A photogravure film is prepared as described in UK. Pat. No. 938,960 by successively applying the following layers to the front side of a polyethylene terephthalate support of 0.10 mm. thickness, the rear side of which is provided with the usual photographic subbing and antihalation layers:

1. A stripping layer from the following composition:

copoly(vinylidene chloridc/acrylonitrile) 20 g.

methylene chloride 250 cc.

ethyl acetate 250 cc.

acetone 530 cc.

2. A support membrane from the following composition:

cellulose nitrate 40 g.

tricresyl phosphate 10 g.

diethyl ether 200 cc.

ethanol 700 cc.

n-butanol 100 cc.

3. a subbing layer from the following composition:

gelatin l g.

salicylic acid 2.5 g.

cellulose triacetate g.

water 32 cc.

ethanol 52 cc.

acetone 710 cc.

methanol l40 cc.

methylene chloride 50 cc.

4. A light-sensitive silver halide emulsion layer which has been applied from a dispersion having the following composition:

orthochromatic gelatino-silver chloride emulsion having a medium gradation and an initial proportion of gelatin to silver nitrate of 2 to l 140 cc.

water I l cc.

% aqueous solution of potassium metabisulfite 3 cc.

dispersion of compound 5 in aqueous gelatin prepared as described in the above preparation I3 26 cc.

B. Formation of an etching resist The light-sensitive material is exposed first through a gravure screen and then through a continuous-tone diaposittve.

Then the material is treated for 3 minutes in a l0 percent aqueous solution of sodium carbonate to initiate development and then fixed in a nonhardening fixing solution having e.g., the following composition:

water 800 cc.

sodium thiosulfate 200 g.

potassium metabisulfite 25 g.

waterup to l,()0()ce.

After washing and drying the material is pressed with its emulsion side against a wetted copper cylinder to which the emulsion adheres. After 1 minute the polyethylene terephthalate support is removed by stripping.

A mixture consisting of 400 cc. of acetone, 500 cc. of ethanol and 100 cc. of water is poured onto the photographic material and after 30 sec. the support membrane of cellulose nitrate is stripped off.

The copper cylinder to which the imagewise tanned emulsion layer adheres is dipped into a bath with warm water of 455O C. and washed for about 15 minutes in order to remove the unhardened gelatin portions. The subsisting etching resist is dried and the copper cylinder can be etched through the resist by means of an aqueous ferric chloride solution.

In a similar way etching resists were prepared using compounds 1. 7, l0 and 12 as tanning developer precursor in the light-sensitive emulsion layer of the photogravure film.

EXAMPLE 3 Preparation of photographic material for line work (document reproduction) To both sides of cellulose tn'acetate support a subbing layer is applied from the following composition:

gelatin l0 g. water 50 cc. maleic acid 3 cc. methanol 750 cc. 4% solution of cellulose nitrate in ethanol/ether lzl) 50 cc. n-butanol 150 cc.

The subbing layer at the rear side of the support is overcoated pro rata of 10-12 g. of solids per sq. m. with an antihalation layer from the following composition:

fuchsine ll) g. water 900 cc. gelatin l0% aqueous solution of saponin 6 cc.

The subbing layer at the front side of the support is overcoated pro rata of 10-14 g. of solids per sq. m. with a silver halide emulsion layer from the following composition:

orthoor panchromatic silver chlorobromide emulsion having an initial proportion of gelatin to silver nitrate of 3-5 to l and having a high gradation cc. dispersion of compound l2 in aqueous gelatin prepared as described in the above preparation l3 18 cc.

The photographic material obtained is exposed through a line negative, treated with an alkali solution such as an 8 percent aqueous solution of sodium carbonate to initiate development and finally washed with warm water of 50 C. whereby the unexposed and consequently unhardened areas are removed and dried.

A diapositive of good quality is obtained.

In a similar way a diapositive was prepared using compound 5 as tanning developer precursor in the light sensitive emulsion layer of the photographic material.

EXAMPLE 4 Preparation of photographic material for continuous-tone work The photographic material is prepared as described in example 3 except that now the silver halide emulsion layer is applied pro rata of 8-12 g. of solids per sq m. from the following composition:

blue-sensitive silver chloride emulsion comprising a yellow screening dye, having a high gradation and having an initial proportion of gelatin to silver nitrate of 3-4 to l dispersion of compound 12 in aqueous gelatin prepared as described in the above preparation l3 18 cc. The photographic material is exposed through the back of its support to a continuous-tone negative whereupon it is treated with an alkali-solution such as an 8 percent aqueous solution of sodium carbonate. Then the material is washed with warm water of 50 C., whereby the unexposed and thus unhardened emulsion area s are remo ved, and dried A continuous-tone positive of high quality is obtained which is free of fog and stain in the high-light areas.

In a similar way a continuous-tone positive was prepared using compound 1 as tanning developer precursor in the lightsensitive emulsion layer of the photographic material.

We claim:

1. A photographic element comprising a support and at least one photographic hydrophilic colloid silver halide emulsion layer, wherein said emulsion layer and/or a hydrophilic colloid layer in water-permeable relationship with said emulsion layer contains an o-dihydroxybenzene silver halide tanning developing agent precursor wherein at least one of the hydroxyl groups has been esterified to form a halogenated acyloxy group or wherein one of the hydroxyl groups has been etherified to form an a-tetrahydropyranyloxy group.

2. A photographic element according to claim 1, wherein said o-dihydroxybenzene silver halide developing agent precursor corresponds to the following general formula:

MELW W wherein:

R represents a haloacyl group, R represents hydrogen or a haloacyl group, and

R represents hydrogen, an alkyl group, a halogen atom, an

alkoxy group, or the group 0R 3. A photographic element according to claim 1, wherein said o-dihydroxybenzene silver halide developing agent precursor corresponds to the following general formula:

wherein:

R stands for an a-tetrahydropyranol group,

R stands for hydrogen,

4. A photographic element according to claim 1, wherein the colloidal binder of each layer incorporating said developing agent precursor is substantially unhardened.

5. A photographic element according to claim 4, wherein said substantially unhardened colloidal binder is gelatin.

6. A process for forming a visible image which comprises exposing a photographic element comprising a support and at least one photographic hydrophilic colloid silver halide emulsion layer, wherein said emulsion layer and/or a hydrophilic colloid layer in water-permeable relationship with said emulsion layer contains an o-dihydroxybenzene silver. halide tanning developing agent precursor wherein at least one of the hydroxyl groups has been esterified to form a halogenated acyloxy group or wherein one of the hydroxyl groups has been esterified to form an a-tetrahydropyranyloxy group and treating the exposed photographic element with an alkaline solution.

7. A process for forming a visible image according to claim 6, wherein the colloidal binder of each layer of the photographic element incorporating said developing agent precursor is substantially unhardened.

8. A process for forming a visible image according to claim 6, wherein said colloidal binder is gelatin.

9. A process for forming a visible image according to claim 7, which comprises the further step of removing unhardened portions of the said layer.

10. A process according to claim 6, wherein said alkaline solution is a mere solution of at least one compound selected from sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3,639 ,l26 Dated February 1, 1.972

Inventor(s) Johan Lodewijk VERELST et al It is eertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 11, Claim 2, in the formula: Change "-IOH" to Column 12, Claim 3, in the formula: Change "OR to Claim 3, line 16, change "on-tetrahydropyranol" to v octetrahydropyranyl Claim 6, line 32, change "esterified" to etherified Signed and sealed this 20th day of June 1972.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. ROBERT GO'ITSCHALK Attesting ()fficer Commissioner of Patents FORM PO-1050 (10-69) USC OMM'DC 60376-P69 U.S. GOVERNMENT PRINTING OFFlCE: I969 0-366-334 

2. A photographic element according to claim 1, wherein said o-dihydroxybenzene silver halide developing agent precursor corresponds to the following general formula: wherein: R1 represents a haloacyl group, R2 represents hydrogen or a haloacyl group, and R3 represents hydrogen, an alkyl group, a halogen atom, an alkoxy group, or the group OR2.
 3. A photographic element according to claim 1, wherein said o-dihydroxybenzene silver halide developing agent precursor corresponds to the following general formula: wherein: R1 stands for an Alpha -tetrahydropyranol group, R3 stands for hydrogen,
 4. A photographic element according to claim 1, wherein the colloidal binder of each layer incorporating said developing agent precursor is substantially unhardened.
 5. A photographic element according to claim 4, wherein said substantially unhardened colloidal binder is gelatin.
 6. A process for forming a visible image which comprises exposing a photographic element comprising a support and at least one photographic hydrophilic colloid silver halide emulsion layer, wherein said emulsion layer and/or a hydrophilic colloid layer in water-permeable relationship with said emulsion layer contains an o-dihydroxybenzene silver halide tanning developing agent precursor wherein at least one of the hydroxyl groups has been esterified to form a halogenated acyloxy group or wherein one of the hydroxyl groups has been esterified to form an Alpha -tetrahydropyranyloxy group and treating the exposed photographic element with an alkaline solution.
 7. A process for forming a visible image according to claim 6, wherein the colloidal binder of each layer of the photographic element incorporating said developing agent precursor is substantially unhardened.
 8. A process for forming a visible image according to claim 6, wherein said colloidal binder is gelatin.
 9. A process for forming a visible image according to claim 7, which comprises the further step of removing unhardened portions of the said layer.
 10. A process according to claim 6, wherein said alkaline solution is a mere solution of at least one compound selected from sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate. 